Channel programming varies by market, but most of the major network stations, including NBC, CBS, ABC, FOX and CW, offer most of their primetime programming in high definition. Other channels with high-definition programming include Telemundo, PBS and Univision. Popular cable channels that offer high-definition channels include Food Network, SyFy, FX, AMC and the History Channel. Premium cable channels, including HBO, Starz, Showtime and Cinemax, also offer high-definition channels.
High-definition channels provide higher resolution images than their standard-definition counterparts, with as many as five times as many pixels onscreen at a time. Unlike standard definition, high definition requires a digital signal, delivered through satellite, cable, Internet-protocol television or other transmission method.
Most high-definition content available from network and cable providers is either 1080i or 720p resolution. 1080p is high resolution and provides twice as many pixels per frame than 1080i, but most 1080p content is streaming and on-demand video.
Manufacturers first sold high-definition televisions in the United States in 1998, though there were no dedicated high-definition channels, and networks broadcast only select major events in high definition, such as the space shuttle Discovery launch and the 2000 Super Bowl. As high definition grew in popularity, satellite services began broadcasting in high definition in 2002 and cable networks in 2003. High definition is the standard for television service in the United States, and only a few providers do not offer high-definition content, as of 2015.